While the Hexanon may be one of the cheapest 50mm lenses it still is "only" 50mm. Nearer to the optimum 67,5mm would be a 58mm lens as the Minolta MC Rokkor 58mm 1,4 which is cheap too or the bokeh version, the expensive 1,2 lens. Annother expensive one would be the Canon FL 58mm 1,1. And a cheaper one the Helios 58mm 2,0 with M42 mount.